Automatically retractable needle syringe



Feb. 28, 1967 H. s. WELTMAN 3,306,290

AUTOMATICALLY RETRACTABLE NEEDLE SYRINGE Filed Feb. 14, 1964 INV ENT ORiqaz'azd 6. Weliman ATTORNEYS United States Patent 3,306,290AUTOMATICALLY RETRACTABLE NEEDLE SYRINGE Harold S. Weltman, 292 S.Franklin St., Wilkes-Barre, Pa. 18702 Filed Feb. 14, 1964, Ser. No.344,996 10 Claims. (Cl. 128218) This invention relates to hypodermicsyringes, or the like, of the type employed by dentists and physiciansfor injecting drugs, and other fluids into body tissues. Moreparticularly, the present invention relates to an improved syringe ofthe type employing disposable carpules as used in the dental professionto inject a local anesthetic.

The hypodermic syringes that are presently used to effect subcutaneousinjections are characterized by a plunger operated device that carries aslender tubular needle through which liquid is passed into body tissue.The tubular needle being exposed to view is subect to accidental damageand contamination during sterilization or while being carried from placeto place and causes apprehension in the patient on seeing the needle.

Accordingly, it is an object of the present invention to provide asyringe with an automatically retractable needle whereby the needle isprotected when not in use thus saving expensive replacement of damagedneedles and providing freedom from contamination and improvedpsychological disposition of the patient by removing the anticipation,apprehension and excitement caused by sight of an exposed needle.

Another object of the invention is the provision of an improved dentalsyringe of the type employing disposable carpules, which is of simple,inexpensive and practical construction and which is easily kept in goodoperating and aseptic condition.

Still another object is the provision of a new and improved hypodermicneedle syringe which is convenientfor dental use and which allowsconcealment and protection of the needle portion of the syringe untilimmediately before insertion into the tissue of the patient whereby theneedle is extended out of the sight of the patient.

Yet another object of the invention is to provide a new and improvedsyringe of the foregoing character that is highly effective, extremelyserviceable and yet easily manufactured at low cost.

Other objects and many of the attendant advantages of the invention willbe readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings in which like referencenumerals designate like parts throughout the figures thereof andwherein:

FIG. 1 is a fragmentary elevational view of a typical preferred form ofmy improved hypodermic syringe;

FIG. 2 is a fragmentary vertical sectional view through the syringe ofFIG. 1 with the needle shown in a retracted position;

FIG. 3 is a fragmentary vertical sectional view similar to FIG. 2 butwith the needle shown in a projected position.

FIG. 4 is an enlarged transversed vertical sectional view taken on theline 4-4 of FIG. 3 and FIG. 5 is a fragmentary vertical sectional viewof a modified form of the hypodermic syringe.

Referring now to the drawings that are shown; in FIG. 1 the hypodermicsyringe 6 of the typical simple cylinder and piston type device and asillustrated is chargeable with a carpule or fluid carrying unit 8 andhaving a plunger 10 adapted to operate against the carpule to ejectfluid therefrom through needle 12.

The body portion of barrel 14 is usually of cylindrical shape and isformed with longitudinal openings or slots 16 on opposite sides thereofallowing view and manipulation of the carpule. A thumb rest 18 ismounted on the back end of the plunger 10 and finger rests 20 aremounted on and are adapted to revolve around head portion 22. Theopposite end of the plunger has stop means 24 which, on extensions ofthe plunger, also act as compressing means for the carpule.

There are various head portions available on different types of syringesthat provide means for supporting the plunger and allow access to thebarrel for insertion of carpules. But the type preferred for thepurposes of the present invention comprise a hollow head portion 22having a central bore 26 to receive plunger positioning means comprisinga tapered cylinder 28 having a central cylindrical bore 30 for receivingthe plunger and being tapered so as to fit a short distance into theback end of the barrel and also adapted to be disposed into the recess26 of hollow head portion 22 when compressed against spring 34 bywithdrawing the plunger. Said head portion has arms 36 rotatably securedto barrel 14 by means of screws 38.

The assembly of this section of the inventive device is accomplished byinserting the cylinder over the plunger, the narrow end of the cylindertoward the stop on the plunger. The spring is then slid over the plungerand the plunger inserted into the head and the thumb rest screwed on theother end of the plunger. The spring is compressed and the holes in thearms of the head aligned with holes provided in the barrel and thescrews inserted. The back part of the syringe is then ready to receive acarpule.

A standard carpule comprises a tubular transparent body 40 containingfluid 42 having a front end comprising a first plug 44- constructed ofpliant type material and adapted to be pierced by the rearward pointedend 46 of needle 12 and a back end comprising a piston type of plug 48.The plugs are preferably of soft pliant material such as rubber so thatthe first plug is penetrable by needle in a sealing engagement and theback plug is compressible to have a sliding and sealing engagement withthe interior of the carpule wall.

The inside front portion of barrel 14 is threaded to receive externallythreaded hub 50. The hub comprises a front tapered portion 52terminating in a rounded point 54 having an exit port. The hollow,externally threaded back portion is adapted to receive needle retractingspring '56 and a bore is provided through the front hub portion to allowextension of the needle. The needle 12 is of the usual doubly sharpenedtype and has a piston disc 58 secured thereto at a suitable midpointallowing travel of said needle from an extended to a retracted positionin its housing in the barrel. The forward travel of said disc and needleis restrained by abutment of the disc on the end of hub 50 and rearwardfrom said hub is provided an enlarged bore section 60 which acts as acylinder for said piston and needle and terminates at stops 62 which isthe start of narrower section 64 of the barrel, which extends along thelength of the carpule 8.

The assembly of the front section of the barrel is accomplished byinserting the needle and piston into the front end of the barrel,placing the spring over the needle and screwing the hub onto the barrel.Insertion of,a carpule is accomplished by completely withdrawing theplunger from the barrel so as to compress the head spring and draw thecylinder into the recess provided in the head of the barrel. The entirehead is then rotated on the arms pivoted at the screws secured to thebarrel thus exposing the back end of the barrel. The carpule is nowinserted into the barrel and the head rotated back to a closed position.The front plug of the carpule may be pierced by the back point of theneedle in one of two Ways. The carpule may be grasped through the slotsin the barrel and moved forward in the barrel until the plug is piercedand seated against the back side of the piston disc of the needle. Thesame effect may be accomplished by exerting pressure on the carpule bymeans of the thumb rest and plunger thus driving the carpule forwarduntil it is seated on the needle. The latter method is preferred sincethe needle may be cleared of air at the same time by expelling a smallamount of fluid. In either case, release of pressure results in theautomatic retraction of the needle and return of the carpule by the biasof the expanding forwardly disposed spring. To inject the fluid, slightpressure on the thumb rest completely extends the needle out of the huband by additional pressure, the rear piston type stopper of the carpulewill be moved forward relative to the walls of the carpule by means ofthe plunger and the fluid contained therein will be expelled from theneedle. Removal of the needle from the injection site and release ofpressure on the thumb rest results in automatic retraction of the needleinto the hub. The head is again broken open and by finger pressurethrough the slots in the barrel, the carpule is removed and the syringeis now ready for sterilization.

The modified embodiment of the invention shown in FIG. has most of theadvantages of the first described structure except the ability toretract the needle once the carpule has been inserted. This device hasthe same forward and back sections and is operated and used in the samemanner. However, the barrel is shortened by an amount equivalent to thecylindrical bore provided for the axial movement of the needle piston.Therefore, on insertion of the carpule, the needle remains permanentlyextended but is automatically retracted during sterilization andhandling so as to protect the needle from accidental breakage or damage.Specifically, this modified embodiment comprises a shortened barrel 66having an internally threaded front end and externally threaded hub 50secured thereto and an axially moveable doubly pointed needle 12 withpiston means 58 disposed in enlarged cylindrical bore 60 in the barrelterminating in stop 62. A carpule retaining narrowed back portion 64 ofthe barrel terminates in rotatable head section 22 carrying plunger andstop member 24, tapered cylinder 28 and head spring 34.

The following is illustrative of a specific embodiment of the invention,it being understood that the relative dimensions are given by way ofillustration only and can be altered to suit particular requirements:

Barrel-Length 3%", CD. /2", ID. of enlarged bore 6 ID. of carpuleretaining section for 2 /8" Hub-Length 0D. /2" from back portiontapering to rounded point Needle Bias Spring-Length, approx. 1 /2"extended, CD. A", 27" gauge wire compressible with about 3-7 ounces ofpressure Needle-Length 2%", approx. 27" gauge; piston disc 0D. /8 fixedat a point 1%" from front point of needle HeadI.D. of bore approx. armsseparated by PlungerLength 9'', OD. 7 CD. of stop member TaperedCylinder-Bore OD. tapered so as to fit into back end of barrel to adepth of about Ms" Head SpringLength /6, LD. about to fit aroundplunger, approx. 25 .gauge wire compressible wit-h about 2 lbs. pressureThumb RestApprox. Vs" D.

Standard 1.8 cc. carpuleLength about 2 /2",

However, it is obvious that by substituting a longer barrel section andplunger, the syringe of the present invention can accommodate both the1.8 cc. and 2.2 cc.

variety of carpules. The main parts of the syringe can be stainlesssteel or chrome plated steel. The piston can be a machined disc or ofthe self lubricating variety of plastics capable of withstandingsterilization temperatures such as a polytetrafiuroethylene,commercially known as Teflon or Kel-F.

Obviously, many other modifications and variations of the presentinvention are possible in the light of the above teachings. It istherefore, to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

I claim:

1. A hypodermic syringe, comprising; an elongated tubular body having afirst bore portion in one end thereof for slidably receiving a tubularcarpule, and a second bore portion at the other end thereof aligned withand adjacent to said first bore portion; manually operable plunger meanscarried by said one end of said tubular body, selectively engageablewith said carpule to slide the same within said tubular body and toeffect selective emptying thereof; a hub mounted on said other end ofsaid tubular body, and having an axial bore therethrough aligned withsaid first and second bore portions; a piston received within saidsecond bore portion, and having a bore therethrough aligned with saidaxial hub bore; a hollow needle pointed at both ends thereof, saidneedle extending through and being secured within said piston bore, andbeing translatable within said axial hub bore, the opposite ends of saidneedle extending for a substantial distance from the opposite sides ofsaid piston; abutment means within said tubular body at the junction ofsaid first and said second bore portions, said piston being engageablewith said abutment means to limit movement of said piston toward saidfirst bore portion and resilient means arranged to bias said piston andsaid needle away from said hub and toward said first bore portion, toengage said piston with said abutment means.

2. A hypodermic syringe as recited in claim 1, wherein said second boreportion is enlarged relative to said first bore portion, and terminatesat the inner end thereof in a shoulder, said shoulder defining saidabutment means.

3. A hypodermic syringe as recited in claim 1, wherein said hub isdetachably secured to said tubular body.

4. A hypodermic syringe as recited in claim 1, wherein said lastmentioned means comprises a coil spring received Within said second boreportion, and extending between said piston and said hub.

5. A hypodermic syringe as recited in claim 1, wherein said plungermeans is arranged to be moveable from a first position in alignment withsaid first bore portion, to a second position wherein the outer end ofsaid first bore position is open to receive said carpule.

6. A hypodermic syringe, comprising: an elongated tubular body having afirst bore portion in one end thereof for slidably receiving a tubularcarpule, and a second bore portion -at the other end thereof alignedwith and adjacent to said first bore portion, said second bore portionbeing enlarged relative to said first bore portion, and terminating atthe inner end thereof in an abutment shoulder; manually operable plungermeans carried by said one end of said tubular body, and engageable withsaid carpule to slide the same forwardly within said tubular body and toeffect selective emptying of said carpule; a hub mounted on said otherend of said tubular body, and having an axial bore therethrough alignedwith said first and said second bore portions; a piston received withinsaid second bore portion, and having a bore therethrough aligned withsaid axial hub bore, said piston being slidable within said second boreportion from a first position in engagement with said abutment shoulder,to a second position spaced from said abutment shoulder; a hollow needlepointed at both ends thereof, said needle extending through and beingsecured within said piston bore, the inner end of said needle projectingfor a substantial distance from the inner face of said piston, and theouter end.

of said needle projecting from the outer face of said piston for adistance such that it will extend substantially beyond the outer end ofsaid axial hub bore when said piston is in said second position, andthat it will be comsecond bore portion, and arranged to extend betweenconfronting surfaces on said hub and said piston.

10. A syringe as recited in claim 9, wherein said coil spring iscompressible with from about 3 to about 7 pletely received within thecombined lengths of said axial 5 ounces of pressure.

hub bore and said second bore portion when said piston is in said firstposition; and resilient means arranged to bias said piston toward saidfirst position thereof.

7. A syringe as recited in claim 6, wherein said plunger means isarnanged to be moveable from a first position in alignment with saidfirst :bore portion, to a second position wherein the outer end of saidfirst bore portion is open to receive said carpule.

8. A syringe as recited in claim 6, wherein said hub is detachablysecured to said tubular body.

9. A syringe as recited in claim 6, wherein said resilient meanscomprises a coil spring received within said References Cited by theExaminer UNITED STATES PATENTS 2,460,039 1/ 1949 Scherer et a1 128 2 l 82,701,566 2/1955 Krug 128218.2 2,752,918 7/ 195 6 Uytenbogaart 128218.23,046,985 7/1962 Saenz 128218.1

FOREIGN PATENTS 164,214 7/ 1955 Australia.

DALTON L. TRULUCK, Primary Examiner

1. A HYPODERMIC SYRINGE, COMPRISING; AN ELONGATED TUBULAR BODY HAVING AFIRST BORE PORTION IN ONE END THEREOF FOR SLIDABLY RECEIVING A TUBULARCARPULE, AND A SECOND BORE PORTION AT THE OTHER END THEREOF ALIGNED WITHAND ADJACENT TO SAID FIRST BORE PORTION; MANUALLY OPERABLE PLUNGER MEANSCARRIED BY SAID ONE END OF SAID TUBULAR BODY, SELECTIVELY ENGAGEABLEWITH SAID CARPULE TO SLIDE THE SAME WITHIN SAID TUBULAR BODY AND TOEFFECT SELECTIVE EMPTYING THEREOF; A HUB MOUNTED ON SAID OTHER END OFSAID TUBULAR BODY, AND HAVING AN AXIAL BORE THERETHROUGH ALIGNED WITHSAID FIRST AND SECOND BORE PORTIONS; A PISTON RECEIVED WITHIN SAIDSECOND BORE PORTION, AND HAVING A BORE THERETHROUGH ALIGNED WITH SAIDAXIAL HUB BORE; A HOLLOW NEEDLE POINTED AT BOTH ENDS THEREOF, SAIDNEEDLE EXTENDING THROUGH AND BEING SECURED WITHIN SAID PISTON BORE, ANDBEING TRANSLATABLE WITHIN SAID AXIAL HUB BORE; THE OPPOSITE ENDS OF SAIDNEEDLE EXTENDING FOR A SUBSTANTIAL DISTANCE FROM THE OPPOSITE SIDES OFSAID PISTON; ABUTMENT MEANS WITHIN SAID TUBULAR BODY AT THE JUNCTION OFSAID FIRST AND SAID SECOND BORE PORTIONS, SAID PISTON BEING ENGAGEABLEWITH SAID ABUTMENT MEANS TO LIMIT MOVEMENT OF SAID PISTON TOWARD SAIDFIRST BORE PORTION AND RESILIENT MEANS ARRANGED TO BIAS SAID PISTON ANDSAID NEEDLE AWAY FROM SAID HUB AND TOWARD SAID FIRST BORE PORTION, TOENGAGE SAID PISTON WITH SAID ABUTMENT MEANS.